1. Field of the Invention
The present invention relates to log debarkers and more specifically to an air-operated log debarker of the rotary ring type.
2. Description of the Prior Art
Many rotary ring-type debarkers have hydraulically operated barking tools with their hydraulic actuating motors and the pressurized hydraulic supply being carried by the rotor. The rotor hydraulic supply is pressurized at the desired pressure level while the rotor is stationary and may be varied slightly during rotation of the rotor through the use of a small electric motor-operated pump on the rotor.
Air pressure-operate barking tools for ring-type debarkers have been proposed to replace the captive hydraulic system described above because an air-operated system is theoretically less complex and faster acting than the hydraulic system. An air system also eliminates the need for carrying a hydraulic supply and pump on the rotor and the need for charging the rotor with fluid when the rotor is stationary since pressurized air can be directed into the rotor from an external source though an appropriate seal while the rotor is operating. However, the use of air to operate the barking tools raises the problem of providing an appropriate air seal that is effective and long-lasting.
Most prior ring-type debarkers using air-operated barking tools require a constant external supply of pressurized air to the rotor to maintain tool-operating pressure during normal operation. This in turn requires the air seals to be in constant sealing engagement while the debarker operates, causing rapid seal wear and thus frequent stoppages for maintenance.
The one ring-type debarker with air-operated tools as exemplified by Hansel U.S. Pat. No. 2,798,519, an air pressure reservoir in the rotor is charged while the rotor is stationary to provide tool-operating air. However, when the debarker is operating there is no way to increase tool or reservoir pressure by adding outside air. Outside air is required to open the tools while the rotor operates, and therefore an air seal is still required.
Other rotary ring debarkers with air-operated barking tools as exemplified by Brown U.S. Pat. No. 3,361,168 employ single-acting air springs to close the tools and apply tool pressure. Centrifugal force is relied on to open the tools, and therefore the tools cannot be opened for maintenance or to clear broken logs while the rotor is stationary. Air for operating the springs to close the tools and maintain tool pressure during normal operation is supplied by one or more air reservoirs in the rotor. Nevertheless, in this type of debarker external air must be continually supplied to the rotor to position rotor valves for supplying air from the reservoirs to the air springs. Thus the rotor air seal must remain continually operative to maintain air pressure on the air springs and barking tools.
In another air-operated debarker utilizing single-acting air springs to apply tool pressure, as exemplified by Bentley et al U.S. Pat. No. 3,667,517, the rotor is pressurized to maintain tool pressure during normal debarker operation while spring-biased valves on the rotor maintain rotor air pressure. However, external air pressure is required to open and close the tools though operation of the aforesaid valves. Also, the rotor must be completely exhausted of air to permit centrifugal force to open the tools. This requires a complete recharging of the rotor with external air upon each closing of the tools. External air is required to apply an air seal upon each tool opening and closing function.
thus in all known ring-type debarkers with air-operated tools, air from an external source must be added either while the rotor is stationary, continually while the rotor operates, or at least both to open and close the tools, requiring constant or at least frequent and prolonged loading and therefore rapid wearing of the air seal. Moreover, the tools of most such debarkers are opened using centrifugal force rather than positive fluid pressure.